An organic electroluminescent device is advantageous in that the device can be built on a transparent substrate, can operate at low voltages of 10 V or below as compared to a plasma display panel or an inorganic electroluminescent (EL) display, consumes relatively less power, provides excellent color quality and can display green, blue and red colors. Accordingly, it attracts a great deal of interests as a next-generation display device.
For the organic electroluminescent device to fully exert the above-mentioned characteristics, a hole injection material, a hole transport material, an electroluminescent material, an electron transport material, an electron injection material, etc. included in an organic layer of the device should be stable and effective. However, development of such stable and effective materials for the organic layer of the organic electroluminescent device is not satisfactory as yet. Accordingly, development of new materials exhibiting operability at low voltage, high efficiency and long lifetime is consistently needed.
As hole transport materials, copper phthalocyanine (CuPc), MTDATA, 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TPD), etc. are known. However, since these materials are problematic in efficiency and lifetime when they are employed in devices, many arylamine-based compounds having various substituents are being developed. But, they are also insufficient to satisfy both the efficiency and long lifetime.